SIRT3 overexpression in rat muscle does not ameliorate peripheral insulin resistance.

Reduced expression of the NAD+-dependent deacetylase, SIRT3, has been associated with insulin resistance and metabolic dysfunction in humans and rodents. In this study, we investigated whether specific overexpression of SIRT3 in vivo in skeletal muscle could prevent high-fat diet (HFD)-induced muscle insulin resistance. To address this, we used a muscle-specific adeno-associated virus (AAV) to overexpress SIRT3 in rat tibialis and extensor digitorum longus (EDL) muscles. Mitochondrial substrate oxidation, substrate switching and oxidative enzyme activity were assessed in skeletal muscles with and without SIRT3 overexpression. Muscle-specific insulin action was also assessed by hyperinsulinaemic-euglycaemic clamps in rats that underwent a 4-week HFD-feeding protocol. Ex vivo functional assays revealed elevated activity of selected SIRT3-target enzymes including hexokinase, isocitrate dehydrogenase and pyruvate dehydrogenase that was associated with an increase in the ability to switch between fatty acid- and glucose-derived substrates in muscles with SIRT3 overexpression. However, during the clamp, muscles from rats fed an HFD with increased SIRT3 expression displayed equally impaired glucose uptake and insulin-stimulated glycogen synthesis as the contralateral control muscle. Intramuscular triglyceride content was similarly increased in the muscle of high-fat-fed rats, regardless of SIRT3 status. Thus, despite SIRT3 knockout (KO) mouse models indicating many beneficial metabolic roles for SIRT3, our findings show that muscle-specific overexpression of SIRT3 has only minor effects on the acute development of skeletal muscle insulin resistance in high-fat-fed rats.

Changing patterns of care for pancreas cancer in Victoria: the 2022 Pancreas Tumour Summit.

BACKGROUND: The Victorian Government convened the second Pancreas Cancer Summit in 2021 to identify unwarranted variation in care 2016-2019, and to assess trends compared with the first Summit 2017 (reporting 2011-2015). State-wide administrative data were assessed at population level in alignment with optimal care pathways across all stages of the cancer care continuum. METHODS: Data linkage performed by Centre for Victorian Data Linkage combined data from Victorian Cancer Registry with other administrative data sets including Victorian Admitted Episodes Dataset, Victorian Radiotherapy Minimum Data Set, Victorian Emergency Minimum Dataset and Victorian Death Index. A Cancer Service Performance Indicator audit was carried out providing an in-depth analysis of identified areas of interest. RESULTS: Of 3138 Victorians diagnosed with pancreas ductal adenocarcinoma 2016-2019, 63% were metastatic at diagnosis. One-year survival increased between time periods, from 29.7% overall 2011-2015 (59.1% for non-metastatic, and 15.1% metastatic) to 32.5% overall 2016-2019 (P < 0.001), 61.2% non-metastatic (P = 0.008), 15.7% metastatic (P = NS). A higher proportion of non-metastatic patients progressed to surgery (35% vs. 31%, P = 0.020), and more received neoadjuvant therapy (16% vs. 4%, P < 0.001). Postoperative mortality following pancreatectomy at 30 and 90 days remained low at 2%. Utilization of 5FU-based chemotherapy regimens increased between 2016 and 2020. Multidisciplinary Meeting (MDM) presentation was still below the 85% target (74%) as was supportive care screening (39%, target 80%). CONCLUSIONS: Surgical outcomes remain world-class and there has been an appropriate shift in chemotherapy administration towards neoadjuvant timing with increasing use of 5FU-based regimens. MDM presentation rates, supportive care and overall care coordination remain areas of deficiency.

Surgical management of breast cancer in Victoria: A state-wide audit.

AIM: The Victorian Tumour Summits are an initiative of the Victorian Integrated Cancer Services to engage clinicians and consumers in identifying unwarranted variations in cancer care across the state. From the analysis presented at the Victorian Breast Tumour Summit in 2021, this study provides a state-wide overview of epidemiology and surgical care of breast cancer in Victoria to outline any variations in care across the state, and limitations in data reporting, which impacts the understanding of breast cancer burden and service planning. METHODS: A retrospective analysis of Victorian breast cancer patients diagnosed between 2016 and 2018 was performed using a linked data set provided by the Department of Health. The linked data sources include Victorian Cancer Registry, Victorian Admitted Episodes Dataset and Victorian Radiotherapy Minimum Data Set, from which patient demographic details, tumor characteristics and treatment records were extracted. Pearson's chi-squared test was used to determine the statistical significance of relationships between various categorical parameters. Variables including demographics, types of surgery (breast-conserving vs. mastectomy), rates of neoadjuvant chemotherapy, and time to surgery were examined. RESULTS: One thousand nine hundred thirty-seven patients with ductal carcinoma in situ and 13,375 patients with invasive breast cancer (IBC) were included. Of 11,351 patients with stages I-III IBC (85%, N = 13,375) 66% underwent breast-conserving surgery (BCS), and 31% underwent mastectomy. The ratio of mastectomy to BCS increased with increasing disease stage. Neoadjuvant chemotherapy was utilized in 11% of early IBC patients who were surgically treated. Eighty-three percent of patients undergoing upfront breast surgery were treated within 5 weeks of diagnosis, with a significant difference in the median time to surgery between public and private sectors. Breast reconstruction was performed in 37% of mastectomy patients, of whom 83% underwent immediate breast reconstruction, and 17% underwent delayed breast reconstruction. CONCLUSIONS: Victorian breast cancer data show a high quality of surgical care coordination. Significant gaps in our data warrant future improvements in the Victorian breast cancer notification system and access to pharmaceutical data for an enhanced understanding of the breast cancer treatment pathways and care delivery.

Population-based analysis of treatment patterns and outcomes for pancreas cancer in Victoria.

BACKGROUND: The Victorian Pancreas Cancer summit 2017 analysed state-wide data on management of Victorians with pancreas cancer between 2011 and 2015 to identify variations in care and outcomes. Pancreas cancer remains a formidable disease but systemic therapies are increasingly effective. Surgery remains essential but insufficient alone for cure. Understanding patterns of care and identifying variations in treatment is critical to improving outcomes. METHODS: This population-based study analysed data collected prospectively by Department of Health and Human services (Victorian state government). Data were extracted from Victorian Cancer Registry (covering all Victorian cancer diagnoses), Victorian Admitted-Episodes Dataset (all inpatient data), Victorian Radiotherapy Minimum Dataset and Victorian Death Index providing demographics, tumour and treatment characteristics, age-standardized incidence, overall and median survival. RESULTS: Of 3962 Victorian patients with any form of pancreatic malignancy, 82% were ductal adenocarcinoma (PDAC), of whom 67% had metastases at diagnosis. One-year overall survival for PDAC was 30% (60% non-metastatic, 15% if metastatic). Median survival with metastases increased from 2.7 to 3.9 months, and from 13.3 to 15.9 months for non-metastatic PDAC between 2011 and 2015. Thirty-one percent of non-metastatic patients underwent pancreatectomy. About 1.5% were treated with neoadjuvant chemotherapy/chemoradiation. Of patients undergoing intended curative resection, 77% proceeded to adjuvant therapy. Fifty-one percent of metastatic PDAC patients never received anti-tumour therapy. CONCLUSIONS: Nearly one-fourth of surgically treated patients never received systemic therapy. More than two-thirds of non-metastatic patients never proceeded to surgery. Further consideration of neoadjuvant therapy should be given to borderline resectable patients. Most patients with PDAC still die soon after diagnosis, but median survival is increasing.

Minimal impact of age and housing temperature on the metabolic phenotype of Acc2-/- mice.

An important regulator of fatty acid oxidation (FAO) is the allosteric inhibition of CPT-1 by malonyl-CoA produced by the enzyme acetyl-CoA carboxylase 2 (ACC2). Initial studies suggested that deletion of Acc2 (Acacb) increased fat oxidation and reduced adipose tissue mass but in an independently generated strain of Acc2 knockout mice we observed increased whole-body and skeletal muscle FAO and a compensatory increase in muscle glycogen stores without changes in glucose tolerance, energy expenditure or fat mass in young mice (12-16 weeks). The aim of the present study was to determine whether there was any effect of age or housing at thermoneutrality (29 °C; which reduces total energy expenditure) on the phenotype of Acc2 knockout mice. At 42-54 weeks of age, male WT and Acc2(-/-) mice had similar body weight, fat mass, muscle triglyceride content and glucose tolerance. Consistent with younger Acc2(-/-) mice, aged Acc2(-/-) mice showed increased whole-body FAO (24 h average respiratory exchange ratio=0.95±0.02 and 0.92±0.02 for WT and Acc2(-/-) mice respectively, P<0.05) and skeletal muscle glycogen content (+60%, P<0.05) without any detectable change in whole-body energy expenditure. Hyperinsulinaemic-euglycaemic clamp studies revealed no difference in insulin action between groups with similar glucose infusion rates and tissue glucose uptake. Housing Acc2(-/-) mice at 29 °C did not alter body composition, glucose tolerance or the effects of fat feeding compared with WT mice. These results confirm that manipulation of Acc2 may alter FAO in mice, but this has little impact on body composition or insulin action.

Subcutaneous fat transplantation alleviates diet-induced glucose intolerance and inflammation in mice.

AIMS/HYPOTHESIS: Adipose tissue (AT) distribution is a major determinant of mortality and morbidity in obesity. In mice, intra-abdominal transplantation of subcutaneous AT (SAT) protects against glucose intolerance and insulin resistance (IR), but the underlying mechanisms are not well understood. METHODS: We investigated changes in adipokines, tissue-specific glucose uptake, gene expression and systemic inflammation in male C57BL6/J mice implanted intra-abdominally with either inguinal SAT or epididymal visceral AT (VAT) and fed a high-fat diet (HFD) for up to 17 weeks. RESULTS: Glucose tolerance was improved in mice receiving SAT after 6 weeks, and this was not attributable to differences in adiposity, tissue-specific glucose uptake, or plasma leptin or adiponectin concentrations. Instead, SAT transplantation prevented HFD-induced hepatic triacylglycerol accumulation and normalised the expression of hepatic gluconeogenic enzymes. Grafted fat displayed a significant increase in glucose uptake and unexpectedly, an induction of skeletal muscle-specific gene expression. Mice receiving subcutaneous fat also displayed a marked reduction in the plasma concentrations of several proinflammatory cytokines (TNF-α, IL-17, IL-12p70, monocyte chemoattractant protein-1 [MCP-1] and macrophage inflammatory protein-1ß [ΜIP-1ß]), compared with sham-operated mice. Plasma IL-17 and MIP-1ß concentrations were reduced from as early as 4 weeks after transplantation, and differences in plasma TNF-α and IL-17 concentrations predicted glucose tolerance and insulinaemia in the entire cohort of mice (n = 40). In contrast, mice receiving visceral fat transplants were glucose intolerant, with increased hepatic triacylglycerol content and elevated plasma IL-6 concentrations. CONCLUSIONS/INTERPRETATION: Intra-abdominal transplantation of subcutaneous fat reverses HFD-induced glucose intolerance, hepatic triacylglycerol accumulation and systemic inflammation in mice.

Overexpression of SIRT1 in rat skeletal muscle does not alter glucose induced insulin resistance.

SIRT1 is a NAD+-dependent deacetylase thought to regulate cellular metabolic pathways in response to alterations in nutrient flux. In the current study we investigated whether acute changes in SIRT1 expression affect markers of muscle mitochondrial content and also determined whether SIRT1 influenced muscle insulin resistance induced by acute glucose oversupply. In male Wistar rats either SIRT1 or a deacetylase inactive mutant form (H363Y) was electroprated into the tibialis cranialis (TC) muscle. The other leg was electroporated with an empty control vector. One week later, glucose was infused and hyperglycaemia was maintained at ~11mM. After 5 hours, 11mM glucose induced significant insulin resistance in skeletal muscle. Interestingly, overexpression of either SIRT1 or SIRT1 (H363Y) for 1 week did not change markers of mitochondrial content or function. SIRT1 or SIRT1 (H363Y) overexpression had no effect on the reduction in glucose uptake and glycogen synthesis in muscle in response to hyperglycemia. Therefore we conclude that acute increases in SIRT1 protein have little impact on mitochondrial content and that overexpressing SIRT1 does not prevent the development of insulin resistance during hyperglycaemia.

Overexpression of manganese superoxide dismutase ameliorates high-fat diet-induced insulin resistance in rat skeletal muscle.

Elevated mitochondrial reactive oxygen species have been suggested to play a causative role in some forms of muscle insulin resistance. However, the extent of their involvement in the development of diet-induced insulin resistance remains unclear. To investigate, manganese superoxide dismutase (MnSOD), a key mitochondrial-specific enzyme with antioxidant modality, was overexpressed, and the effect on in vivo muscle insulin resistance induced by a high-fat (HF) diet in rats was evaluated. Male Wistar rats were maintained on chow or HF diet. After 3 wk, in vivo electroporation (IVE) of MnSOD expression and empty vectors was undertaken in right and left tibialis cranialis (TC) muscles, respectively. After one more week, insulin action was evaluated using hyperinsulinemic euglycemic clamp, and tissues were subsequently analyzed for antioxidant enzyme capacity and markers of oxidative stress. MnSOD mRNA was overexpressed 4.5-fold, and protein levels were increased by 70%, with protein detected primarily in the mitochondrial fraction of muscle fibers. This was associated with elevated MnSOD and glutathione peroxidase activity, indicating that the overexpressed MnSOD was functionally active. The HF diet significantly reduced whole body and TC muscle insulin action, whereas overexpression of MnSOD in HF diet animals ameliorated this reduction in TC muscle glucose uptake by 50% (P < 0.05). Decreased protein carbonylation was seen in MnSOD overexpressing TC muscle in HF-treated animals (20% vs. contralateral control leg, P < 0.05), suggesting that this effect was mediated through an altered redox state. Thus interventions causing elevation of mitochondrial antioxidant activity may offer protection against diet-induced insulin resistance in skeletal muscle.